Issued April 2, 1913. 

U. S. DEPARTMENT OE AGRICULTURE. 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 278. 

B. T. GALLOWAY, Chief of Bureau. 



FLORAL ABNORMALITIES IN MAIZE. 



BY 



JAMES H. KEMPTON, 

Assistant in Crop Acdimatizaiion and Adaptation Investigations. 




WASHINGTON: 

GOVICRNMENT PRINTING OFFICE. 

1913. 



Wororri^,, 



Issued April 2, 1913. 

U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 278. 

B. T. GALLOWAY, Chief of Bureau. 



FLORAL ABNORMALITIES IN MAIZE. 



BY 



JAMES H. KEMPTON, 

Assistant in Crop Acclimatization and Adaptation Investigations. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1913. 



a\ 






BUREAU OF PLANT INDUSTRY. 



Chief of Bureau, Beverly T. Galloway. 
Assistani Chief of Bureau, William A. Taylor. 
Editor, J. E. Rockwell. 
Chief Clerk, James E. Jones. 



Crop Acclimatization and Adaptation Investigations. 

scientific staff. 

O. F. Cook, Bionomist in Cliarije. 

G. N. Collins, BoUniist. 

H. Pittier, Special Field Agenf. 

Albert T. Anders, G. B. Gilbert, J. II. Kinslor, Cbarles G. Marshall, and 1>. .\. Saunders, 

Afjenls. 
Charles H. Clark, C. B. Doyle. James H. Kempton, and R. M. Meade, Ai^sistanls. 
Robert A. Gorham and Walton G. Wells, Student Assistants. 



D. OF D. 
APR 12 1913 



ADDITIONAL COPIES of this publication 
-Li. may be procured from the Superintend- 
ent of Documents, Government Printing 
Office, Washington, D. C. , at 5 cents per copy 



D 



LETTER OF TRANSMITTAL 



U. S. Department of Agriculture, 

Bureau of Plant Industry, 

Office of the Chief, 
Washington^ D. 6'., November 25, 1912. 
Sir: I have the honor to transmit herewith a paper entitled '• Floral 
Abnormalities in Maize," by Mr. James H. Kempton, Assistant in 
Crop Acclimatization, and to recommend its publication as Bulletin 
No. 278 of the Bureau series. 
Respect full}', 

B. T. (jalu)way. 

Chief of Bureau. 
Hon. James AVilson, 

Secretary of Agriculture. 

278 8 



CONTENTS. 



Pago. 

Introduction 7 

Normal inflorescence 7 

Abnormal pistillate spikelets 8 

Abnormal staminate spikelets 10 

Inversion of seeds on the ear 10 

Occurrence of seeds in the tassel of pod corn 12 

Connate seeds 12 

Polyembryony 13 

Evolutionary significance of abnormalities 14 

Conclusions 15 

Description of plates 18 



ILLUSTRATIONS. 



PLATES. 

Page. 
Plate I. Fig. 1 . — Two seeds from a single maize spikelet. Fig. 2. — Germinated 
connate seeds. Fig. 3. — A seed with two embryos. Fig. 4. — 
Paired male and female spikelets from an ear of maize. Fig. 5. — 

Connate seeds in the Hopi variety of maize 18 

II. Seeds from an ear of Zea tunicata 18 

TEXT FIGURES. 

Fig. 1. Section of an ear of maize, showing the arrangement of seeds 8 

2. Diagram of a cross section of two connate maize seeds 13 



B. P. I.— 801. 



FLORAL ABNORMALITIES IN MAIZI- 



INTRODUCTION. 

Indian corn {Zea mays) belongs to a species which has no near 
relatives among either wild or cultivated plants. It has been under 
domestication for so long a period and has become so profoundly 
modified in structural characters that there is now much uncertainty 
as to its nearest affiliations. In its floral characters, particularly, 
the modifications have been so great that the structural analogies 
with other grasses have remained rather obscure. This is particu- 
larly true with respect to the pistillate inflorescence. 

The study of abnormal forms and displaced parts is one of the 
best methods of tracing the evolutionary history of a plant. In Zea 
mays abnormal forms are of common occurrence, and it is seldom 
indeed that several distinct abnormalities are not found wdien even a 
few plants are carefully examined. They occur most frequently in 
varieties that have had little or no selection, probably because most 
abnormalities are in the nature of undesirable reversions and so have 
been suppressed in w^ell-bred strains as the result of selection. They 
can be brought into expression again by inbreeding or by crosses 
between widely different types. 

NORMAL INFLORESCENCE. 

The following brief description of the normal inflorescence in 
maize will serve as a basis for indicating more clearly the nature of 
the structural abnormalities to be described in detail. 

The spikelets of the staminate inflorescence occur in pairs, of which 
one spikelet is sessile and the other is stalked, except in Zea hirta^ 
where there usually are six spikelets borne together, and all are 
sessile. Each spikelet bears two flowers, each of which is provided 
with a glume, a lemma, a palea, a lodicule, and three versatile 2-celled 
stamens. 

The spikelets of the pistillate inflorescence are also borne in pairs, 
but on relatively short pedicels of nearly equal length, eacli pair 
being located in an alveolus. The paired spikelets are ordinarily 

278 , 7 



8 



FLORAL ABNORMALITIES IN MAIZE. 



arranged in double longitudinal rows, the adjoining pairs alternating 
Avith each other. (Fig. 1.) At least one variety of sweet corn, and 
frequently individuals of all varieties, -show exceptions to this rowed 

arrangement of the spike- 
lets. In these exceptions 
the spikelets are arranged 
indiscriminatelv, bearing 
seeds usually of the " shoe- 
peg " type. 

Unlike the stamina te 
spikelet, the pistillate 
spikelet normally bears 
but one flower, the ovary 
of the second flower being 
completely aborted. The 
fertile flower develops into 
a seed of which the em- 
brj^o is borne on the side 
toward the apex of the in- 
florescence. Like the stam- 
inate flower, each pistil- 
late flower has a glume, a 
lemma, and a palea, but the 
loclicule. if it occurs, has 
never been observed. The 
bracts are much reduced in 
size in all except the pod 
corn (Zea tunicata), where 
they are greatly enlarged 
and entirely surroimd each 
seed. 

The abortion of one of 
the flowers of the pistillate 
spikelet does not affect the 
development of its normal 
equipment of bracts. Con- 
sequentl}^ each seed is ap- 
parently equipped with six bracts, though as a matter of fact three 
of these bracts properly belong to tlie aborted flower. 

ABNORMAL PISTILLATE SPIKELETS. 




^ /3 A 



Fig. 1. — Section of an ear of maize, showing the 
arrangement of seeds. The straight line B is 
tlie division between opposite seeds representing 
the same pair of spilielets. The zigzag lines A A 
show the alternation between double rows of 
seeds that represent paired spikelets. 



In a variety of corn grown by the Hopi Indians in Arizona it was 
observed by Mr. G. N. Collins that some of the kernels on the ear 
were apparently inverted ; that is, instead of bearing the embryo on 

278 



ABNORMAL PISTILLATE SPIKELETS. 9 

the side of the kernel toward the apex of the cob it was borne on the 
side toward the base. It was first assumed that this inversion was 
due to a crowding of the kernels on the ear. Since then, however, a 
similar phenomenon has been observed in several other cases, one of 
which was in Zea tanicutd. The dissection of an ear of this latter 
type suggested the true explanation. In this ear it was observed 
that in several instances both of the ovaries in a si)ikelet had devel- 
oped into seeds. (See Pis. I and II.) 

In these cases the kernels were always found back to back, with 
the inverted kernel always coming from the lower flower. This dis- 
covery on the ear of pod corn suggested that this was also the ex- 
planation of the other cases of inverted seeds which had not been 
dissected, owing to the difficulty of removing the spikelets entire. 
A few dissections of the inverted seeds in the Hopi variety were ob- 
tained on further trial, which showed in nearly every case that the 
spikelets had developed seeds from both flowers, the seeds from 
the lower flower being inverted. 

In all the examples in which one inverted seed was found alone in 
the spikelet traces of the upper flower could be seen, showing that the 
inverted seed developed from the lower flower, the upper one l)eing 
aborted. 

In a large number of instances this development, two kernels on 
one spikelet, was accompanied by the abortion of both flowers of the 
other spikelet of the pair. This, however, was not always the case, 
as a few examples were found with two kernels in one spikelet and 
one in the other, and one case where all four floAvers of the paired 
spikelets produced seed. (See PI. II.) The kernels w^ere usually 
of the same size, though cases were noticed where the seed from the 
lower flower was smaller. Both seeds germinate equally well and 
produce seedlings of nearly the same vigor. 

The ear of Zea tiinicata with inverted seeds Avas found among the 
ears harvested from a planting made in 1911. This ear had been 
fertilized Avith pollen from the Hopi variety. In a careful examina- 
tion of 25 original ears groAvn by the Hopi Indians of Arizona G 
Avere found Avith inverted seeds. A single inverted seed was also 
found in an ear of a complex hybrid made up of varieties from 
China. Salvador, and ^lexico. The greatest number of inverted seeds 
or 2-floAvered spikelets found on any one of these ears Avas three, on 
one of the ears of the Hopi varietA^ In 1912 the ear of Zea tunieata 
that had been hybridized Avith the Hopi variety Avas planted to ob- 
serA'e the frequency of the occurrence of the 2-floAvered female spike- 
lets. A critical examination of the 16 ears resulting from this plant- 
ing failed to reveal any iuA'erted seeds. 
71322°— Bull. 27.S— 13 2 



10 FLORAL ABNORMALITIES IX MAIZE. 

ABNORMAL STAMINATE SPIKELETS. 

It was observed that among the phmts there were several having a 
few female flowers in the male inflorescence. In these cases the ovary 
was produced in the upper flower of the sessile spikelet, the lower 
flower of this spikelet, as well as both flowers of the pediceled spike- 
let, remaining staminate. Most of the flowers which bore ovaries 
were perfect or nearly so. though the stamens were sometimes fewer 
than the normal number and were often sterile. 

In all the cases observed where the stamens were fertile they were 
always three in number. Fertile stamens Avere never found in a 
floAver having any sterile stamens; a flower either had fertile or 
sterile stamens, never both, and Avhere fertile they were always of 
the normal number, three. 

A few tassels bore on the lateral branches spikelets having tAvo 
ovaries, one from each of the floAvers. These Avere always in the 
sessile spikelet, the pediceled spikelet having both floAvers staminate. 
This fact seems to indicate that the aborted spikelet Avhich Avas found 
on the ear where two seeds had developed in the other spikelet of the 
pair probably corresponds to the pediceled spikelet of the pair. 

litis ^ has observed that the sessile spikelet in the staminate in- 
florescence of maize is the first to change in sex, but he does not go 
farther and state Avhich floAver of this spikelet is the first to undergo 
the change. The fact that the seeds developed from the loAver floAver 
are always inA^erted seems to indicate that it is the upper flower of 
the spikelet Avhich normally changes sex first. The change Avo-tdd 
then take place in the upper floAver of the sessile spikelet first, fol- 
lowed by the upper flower of the pediceled spikelet, then the lower 
flower of the sessile spikelet, and lastly the loAver floAver of the 
pediceled spikelet. 

The sessile spikelets having tAvo ovaries also had stamens, usually 
one or tAvo, and rarely three, in each floAver, but these Avere neA-er fer- 
tile. Only a fcAv of these 2-floAvered female spikelets produced seeds, 
though all Avere Avell pollinated artificially. These seeds were always 
back to back, both germs facing out, though they Avere not borne 
longitudinally Avith respect to the rachis, one Avith the germ toAvard 
the tip and the other Avith the germ toAvard the base, as is the case 
where they are found on the ear. 

INVERSION OF SEEDS ON THE EAR. 

Included in the planting of experimental corn iu 1012 Avere two 
rows of Zea tunicata. One row Avas from the same lot of seed which 
had in 1911 produced the one ear having iuA'erted seeds. The other 

1 litis, Hugo. Ueber einige bei Zea mays L. beobachtete Atavismen. Zeitschrift fiir 
Induktivo Abstammungs- und A'ererbungslchre, Bc1. 5, 1011, p. 38-57. 
278 



INVERSION OF SEEDS OX THE EAE. 11 

row was from an ear of another strain that had been self-pollinated in 
1911. None of the 16 ears of this latter strain grown in 1911 showed 
inverted seeds, nor did the original ear. 

The seed from the strain that in 1911 produced the ear with in- 
verted seeds had in 1912 tassels with a few inverted seeds, but showed 
no inverted seeds in the 30 ears that were produced. 

The row from the self-fertilized ear of the other strain produced 
SO plants, of which 8 had ears with inverted seeds, or 2-flowered 
spikelets. (See PI. II.) Four ears were dissected and counts made 
of the number of 1 -flowered and ^-flowered spikelets, the results 
being shown in Table I. 

Table I. — Number of female spikelets iritli one and tiro flowers. 



Plant No. 




Two 
flowers. 



1 534 23 

2 495 16 

3 (ear 1 ) , , 471 10 

3 (ear 2) 524 48 



In three of these ears almost all of the 2-flowered spikelets were 
found within 10 centimeters of the tip of the ear. On the second ear 
of plant 3, however, the 2-flowered spikelets were well distributed 
throughout the entire ear. 

The tendency for the ears of maize to bear a staminate spike is a 
well-known phenomenon. The occurrence of 2-flowered spikelets 
near the apex and the tendency for an ear to have a staminate spike 
may be taken as a general indication that the tip is less completely 
specialized. The fact that the second ear had more 2-flowered spike- 
lets, as well as a more even distribution over the ear, is also in accord- 
ance with this view, as the ears tend to become more like branches 
with staminate tips as they near the base of the plant and are there- 
fore more likely to vary in floral structure. Unfortunately, there 
was only the one 2-eared plant that had 2-flowered spikelets on the 
ears, so it was impossible to ascertain whether the behavior of the 
second or lower ear on plant 3 was merely due to chance or was of 
regular occurrence. 

\Vlien the spikelets of the male inflorescence produce female 
flowers, a greater proportion of these spikelets produce two flowers 
than of those on the pistillate inflorescence. This would account for 
the occurrence toward the tips of the ears of more 2-flowered spike- 
lets as the tips tend to become staminate. although staminate tips have 
never been found in pod corn. 

278 



12 FLORAL ABNORMALITIES IN MAIZE. 

OCCURRENCE OF SEEDS IN THE TASSEL OF POD CORN. 

Several of the jilants in the same row that produced the ears with 
2-flowered spikelets also had greatly enlarged tassels which bore a 
large number of pistillate flowers. These plants produced no ears, 
but instead bore all their seeds in the tassel. Three of these tassels 
were dissected and counts made of the 1 -flowered and 2-flowered 
female spikelets. It Avill be noticed that these tassels produced fully 
as many seeds as a fair-sized ear. The counts are shown in Table II. 

Table II. — yurnher of staniincitc sinkclcts ivitli one and tiro piistilUitc flowers. 



Tassel No. 


One 
flower. 


Two 

flowers. 


1 . 


477 


95 


2 


828 
468 


49 


3 


122 







In tassel 1 there was one spikelet that had three well-developed 
seeds. This spikelet had the normal number of glumes, lemmas, 
and paleie. This would seem to indicate that it was not a combina- 
tion of two spikelets, as has been noticed in the staminate flowers 
where the number of glumes, lemmas, and palea* are often more 
than the normal number. A tendency for the spikelets to become 
many flowered has often been noticed in the staminate flowers, 
where as many as 15 stamens have been found in one spikelet, the 
normal number being C. 

CONNATE SEEDS. 

Another fact connected with the normally aborted ovary is that 
in many cases other than pod corn, when both seeds from the same 
spikelet develop, they are united back to back, making Avliat re- 
sembles one seed with two germs on opposite sides. These connate 
seeds would be regarded as 2-seeded fiiuts if a strict botanical in- 
terpretation were given their structure, for they are inclosed in a 
single pericarp. The seed coat proper remains separate and only 
partially surrounds the individual seeds, penetrating the place of 
union for only a short distance and then disappearing completely. 
The corneous layer, which surrounds an amylaceous interior in most 
seeds of the dent type, only partially surrounds the amylaceous por- 
tion of these connate seeds. This amylaceous interior of the connate 
seeds is Avithout any line of demarcation. (Fig. 2.) 

The connate seeds are usually about twice the size of the single 
seeds on the same ear, though sometimes the seed developed from the 
lower flower is smaller. Unfortunately there were not enough con- 
nate seeds to determine the difference in weight between these and 
single seeds. The tAvo halves germinated at about the same time and 

278 



POLYEMBEYONY. 



13 



produced seedlings of equal vigor. Here, too, the number of seeds 
available for the germination test was too small to determine defi- 
nitely whether the seeds always germinate at the same time and have 
equal vigor. 

The union of the seeds wdiich develop from the 2-flowered spikelets 
appears to take place very early, since it is to be observed that the 
two styles or silks are usually united. (PI. I, fig. 5.) 

There have been no cases observed of two maize seeds growing 
together except where both have been produced by one spikelet. 
In pod corn the seeds produced in 2-flowered spikelets are never 
united, owing perhaps to the larger and earlier development of the 
bracts which surround each seed. 



eM3Ryo. 




.EMB^yO 
..£7\/DOSP£/?M 
y\LEUROA/£: LAYER 
_ F'ER/CARP 



Fig. 2. — Dlagi-am of a cross section of two connate maize seeds. 

A large number of the seeds produced from 2-flowered spikelets 
in the Hopi variety were of the connate type, as were several from 
a Hopi X Mexican X Chinese hybrid. The union of the seeds was 
sometimes very striking when the two seeds differed in the color of 
the aleurone layer. 

POLYEMBRYONY. 

The connate kernels are an entirely distinct phenomenon from 
kernels with double embryos, two of which have been found by Mr. 
W. L. Goss, who has charge of the germination work of the Seed 
Laboratory of the United States Department of Agriculture. In 
these cases the kernels Avere of normal size and shape, but had ex- 
ceptionally large germs, which produced two vigorous seedlings. 
The seeds with double embryos were not dissected, but were planted 

278 



14 FLORAL ABNORMALITIES IN MAIZE. 

in the greenhouse, as they were found in January. They were de- 
stroyed by worms between Saturday night and Monday morning, 
when the greenhouses were without care. Mr. Goss has found only 
two of these seeds in the many thousands he lias germinated. There 
Avas no appreciable difference between the two seedlings, as will be 
seen in Plate I, figure 3. 

EVOLUTIONARY SLGNIFICANCE OF ABNORMALITIES. 

The origin of Zea mans is uncertain. It is believed by some bot- 
anists to have developed from an extinct group of grasses, while 
others believe it to be developed from a well-known group. It is 
within the limits of possibility that there are as yet undiscovered 
types able to multiply themselves and to exist in the wild state that 
are perhaps intermediate in form between Zea and its nearest known 
relative, Euchlaena. There can be little doubt that the varieties now 
commonly known would soon become extinct if left to reproduce 
themselves without the assistance of man. 

We know that the aboriginal Americans grew^ corn with much less 
care than is now given to its culture, but with them it never reached 
its present efficiency in the yield of grain. It is evident that in in- 
creasing the efficiency of the maize plant the ability to hold its own 
in a wild state has been completely lost. It is not unreasonable to 
suppose that maize was much less difficult to grow 400 years ago, 
when the Europeans first began its culture. There probably is to be 
found among some of the isolated tribes of Indians in Mexico or Cen- 
tral America types of corn more nearly like the original wild plant 
upon which the first Indian culture was based. The methods of 
culture used by these isolated tribes have probably remained un- 
changed, though better forms may have arisen by unconscious selec- 
tion and modified their primitive types. 

The tendency of evolution is toward complicated types with more 
highly specialized parts. Sudden and abnormal changes are usually 
looked upon as reversions, while the development of new characters 
is attributed to the slower method of selection. Accepting this view, 
the frequent development of 2-flowered female spikelets on the pistil- 
late inflorescence of Zea mays has a significant bearing on its uncer- 
tain evolution. 

There is a striking resemblance in vegetative characters between 
Zea mays and certain members of the Andropogonea?, but the normal 
floral parts are very different in structure and location. From the 
common abnormalities and variations in the floral organs of maize 
a continuous series can be arranged connecting the Maydeae and 
Andropogonefie. 

The chief floral difference between the Maydea? and the Andro- 
pogonea? is that the Andropogonea? normally have androgynous 

278 



CONCLUSIONS. 15 

flowers, while the flowers of the Mayclese are usually unisexual. 
This difference, which has been used to divide the two tribes, is not 
fundamental as far as Zea mays is concerned. One species, Zea 
tunicata, conpnonly has plants that bear a terminal inflorescence com- 
posed of spikelets, a large percentage of which are perfect flowered. 
In other species of Zea adverse external conditions often result in 
androgynous flowers being produced in the male inflorescence. The 
character, wdiich environment changes so essentially in form and 
Avhicli appears as a normal character in some of the plants of Zea 
tunicata, can hardly serve to keep Zea mays and some members of 
the Andropogonese separated. 

Neither Euchlaena nor Tripsacum normally have S-flowered female 
spikelets, though in both of these the male spikelets are ^-flowered, 
as in Zea mays. The examination of a large number of ears result- 
ing from hybridizing Euchlaena and Zea revealed one inverted seed. 
In this case the upper flower of this spikelet Avas aborted, though 
traces of it could be seen. 

From the fact that neither Euchlaena nor Tripsacum have 2- 
flowered female spikelets, we are led back into the Andropogoneae, 
where the next nearest relatives are found. 

Haockel, Goebel, and others have called attention to the clnce 
resemblance of Zea mays to certain members of the Andropogonea?, 
chiefly on account of the frequent occurrence of androgynous flowers. 
The occurrence of S-flowered female spikelets on the pistillate and 
staminate inflorescence, wdiile less frequent than the occurrence of 
androgynous flowers, would seem to be of equal importance in 
strengthening the relation of Zea mays to the Andropogonese. 

CONCLUSIONS. 

Inverted seeds have been found on the male and female inflo- 
rescences of maize. 

These inverted seeds are developed from the loAver flower of the 
spikelet, which is normally aborted. 

Flowers having ovaries and stamens always had the normal namber, 
three, if the stamens were fertile. 

Flowers having both ovaries and sterile stamens often had less 
than three stamens. Fertile and sterile stamens were never found 
in the same flower. 

Spikelets with two ovaries never had any fertile stamens, but some- 
times had from one to three sterile stamens. 

The occurrence of a larger percentage of '2-flowered spikelets near 
the tip of the female inflorescence may be taken to indicate that the 
tip of the ear is less highly specialized than the remainder of the ear. 

That there is a well-defined tendency for both male and female 
spikelets to become many flowered is evidenced by the fact that one 

278 



16 FLORAL ABNORMALITIES IN MAIZE. 

spikelet has been found with three seeds, and male spikelets with 
many more than the normal number of stamens are of common 
occurrence. 

The development of two ovaries in one spikelet is not definitely 
correlated with the abortion of the other spikelet of the pair. A few 
cases have been found where four seeds have developed from the two 
spikelets of a pair and many pairs that have produced three seeds. 

The development of two ovaries in one spikelet must be simul- 
taneous, as a large number of cases have been found where the tw^o 
seeds from one spikelet have grow^n together with a single pericarp. 
These connate seeds had been fertilized through a double silk which 
was attached to the pericarp near the union of the two seeds. 

Connate seeds are a distinct phenomenon from single seeds with a 
double embryo, two of Avhich have been seen. 

The development oi 2-fiowered female spikelets is looked upon as a 
reversion to a more primitive type, the tendency of evolution being 
toward more complicated types with more highly specialized parts. 

Neither Euchlaena nor Tripsacum, the two nearest known relatives 
of Zea mays, have 2-flowered female spikelets, and the occurrence of 
this character in maize is held to strengthen the relationship between 
Zea and the Andropogonea^, already indicated by the occurrence of 
androgynous flowers. 

278 



PLATES. 



>78 



17 



DESCRIPTION OF PLATES. 

Plate I. Fig. 1. — Two seeds from a single spikelet showing eqnal development 
of the young seedlings. Fig. 2. — Germinated connate seeds showing equally 
developed seedlings from both germs. Fig. 3. — A polyembryonic seed from 
a commercial variety of maize. Fig. 4. — Paired spikelets from an ear of 
maize. It will be observed that one spikelet has remained sessile and pis- 
tillate, while the second spikelet has become pediceled and staminate. 
Fig. 5. — ^A group of connate seeds from an ear of the Hopi variety of maize. 
The ear from which these seeds were taken was grown by the Indians on 
their reservation in Arizona. In the center of the left-hand connate seeds, 
in the middle row, the place where the fasciated silk was attached is 
plainly visible. The pollen tubes which fertilized the two embryos must 
both have entered at this point. One half of these connate seeds was a 
bright yellow, while the other was a deep blue. It will be noticed that the 
division between the two members of these connate seeds is always diagonal. 

Plate II. — A group of seeds from an ear of pod corn {Zea tunicata). The 
four seeds in the upper row are from two spikelets. The embryos, it will 
be observed, are on opposite sides. The six seeds in the second row are 
from four spikelets. The two seeds on one stalk in each group are from 
one spikelet. The single seed on a stalk is from the other spikelet of the 
pair. This is also true of the three left-hand seeds in the third row from 
the top. The four seeds on the right hand of the third row from the top 
have developed from two paired spikelets, showing that the development 
of the lower flower into a seed is not always accompanied by the abortion 
of any of the flowers, though one spikelet of the pair is often aborted. 
The figure at the bottom shows a section of the cob with all but four seeds 
removed. The two seeds at the left are from spikelets, each on a separate 
stalk. The other two seeds at the right are both on one pedicel and one is 
hiverted. These seeds both came from one spikelet and reiiresent the 
upper and lower flowers. The seed on which the embryo is visible is from 
the lower flower. 

278 
18 

O 



Bui, 278, Bu'eau ot Plant Industry, U. S. Dept. of Agriculture, 



Plate I. 








Fig. 1.— Two Seeds from a Single Maize Spikelet. (Natural Size, i Fig. 2.— Ger- 
minated Connate Seeds. (Natural Size.) Fig. 3.— A Seed with Two Embryos. 
(Natural Size.) Fig. 4.— Paired Male and Female Spikelets from an Ear of 
Maize, i Enlarged 1'l' Diameters.) Fig. 5.— Connate Seeds in the Hopi Vari- 
ety of Maize; c Indicates Position of Embryo. (Enlarged 1'j Diameters.) 



Df Plant Industry, U. S. Dept. of Agricuitu 



Plate II. 




Seeds from an Ear of Zea Tunicata. 

Figs 1 and 2.— Pairs of seeds eacli from a single spikelet; c, indicates position of embryos. 
Figs. 3 and 4.— a, One seed from a spilielet with germ toward ape.xof ear; 6, two seeds 
from a spilielet witli embryos on opposite sides. Fig. 5.— o, Two seeds from a single 
spikelet, both on one pedicel; 6, a single seed from one spikelet. Fig. 6.— Paired spike- 
lets which have each developed two .seeds, a. Inverted seed developed from lower 
flower; 6, seed developed from npper flower. Fig. 7.— Section of cob. «, Normal de- 
velopment of .seeds from a pair of spikelets, each on a separate pedicel; 6, two seeds 
from a single spikelet, both on a single pedicel. (Enlarged about U diameters.) 



mS^"^ of congress 

HP. 



